The continuous development of mobile communication systems has recently concentrated on post-3G systems, i.e. to the evolution of the 3GPP networks towards the “future” generation of mobile communication networks. There are many initiatives and development projects currently working on the issue, one of them being the Evolved Packet System (EPS), which is being specified in 3GPP release 8. The Evolved Packet Core (EPC) is expected to attach to various access networks, e.g. to UTRAN (Universal Terrestrial Radio Access Network), E-UTRAN (Evolved), GERAN (GSM EDGE Radio Access Network) and non-3GPP access networks. The EPS is specified as a packet-switched-only network and therefore, packet data handling needs to be optimised in the base design.
One of the key areas in the optimisation of packet data handling is the IP address management. During the planned deployment time frame of Release 8 networks and terminals, the transition from the Internet Protocol, version 4 (IPv4) to the Internet Protocol, version 6 (IPv6) is expected to ramp up. This transition phase needs to be supported in the Release 8 specifications.
Currently, Release 8 specifications support PDP (Packet Data Protocol) types IPv4 and IPv6 only for interworking and backwards compatibility purposes. Release 8 MMEs (Mobility Management Entity) and SGSNs (Serving GPRS Support Node) utilise only one PDP type v4v6 for all EPS bearers/PDP contexts. However, despite this modelling principle, any UE or EPS network element may support v4 only, v6 only or v4+v6 IP addressing. Consequently, the network operator may not be able to support IPv6 addressing in all parts of the network, for example in all PDNs, at least in early EPS deployment phase. Furthermore, even though a particular network operator would support IPv6 addressing in all parts of its own network, it cannot be guaranteed that a roaming network and its so-called legacy SGSNs would also support IPv6 or IPv4v6 addressing. Therefore, information about this should preferably be indicated to the UEs.
The U.S. Pat. No. 7,701,958 “Communication system supporting transition between network communication protocols” by Nischal et al discloses a system, wherein a network communication device implementing a dual IPv4/IPv6 stack acquires an IPv4 address only when necessary to communicate with IPv4 resources on the network. The network communication device uses an IPv6 address at the start of a communication session, and does not acquire an IPv4 address unless a need arises later in the session for communication with an IPv4 resource.
However, regardless the fact that the document describes the general idea of the conservation of the IPv4 address, it does not explain how the UE would know when to utilise this scheme.